1. Field of the Invention
This invention relates to a system and a method for processing positioning signals to estimate an acceleration of an embedded timing signal, so as to improve the performance of a positioning function.
2. Discussion of the Related Art
Changes in frequency can reduce the signal-to-noise ratio in a measured positioning signal, typically acquired by calculating a correlation between the positioning signal and a locally generated replica. This reduction in signal-to-noise ratio is particularly relevant in a system in which a coherent correlation is calculated over a long time period. Hence, there is a need for a method and a system to estimate the variations of the clock's frequency. In addition, there is a need for a method and a system that uses these estimated variations to improve processing of the positioning signals.
The following co-pending U.S. patent applications (“Co-pending Patent Applications”) assigned to the Assignee of the present patent application disclose relevant signal processing techniques:                1. Signal Acquisition using Data Bit Information, Ser. No. 09/888,228, filed Jun. 22, 2001, now U.S. Pat. No. 6,512,479, issued Jan. 28, 2003 (hereafter, “Application 228”);        2. Synthesizing Coherent Correlation Sums at One or Multiple Carrier Frequencies Using Correlation Sums Calculated at a Coarse Set of Frequencies, Ser. No. 09/888,227, filed Jun. 22, 2001 (hereafter, “Application 227”);        3. Extracting Fine-Tuned Estimates from Correlation Functions Evaluated at Limited Number of Values, Ser. No. 09/888,338, filed Jun. 22, 2001, (hereafter, “Application 338”);        4. Determining the Spatio-Temporal and Kinematic Parameters of a Signal Receiver and its Clock by Information Fusion, Ser. No. 09/888,229, filed Jun. 22, 2001 now U.S. Pat. No. 6,542,116, issued Apr. 1, 2003 (hereafter, “Application 229”);        5. Determining Location Information Using Sampled Data Containing Location-Determining Signals And Noise, Ser. No. 09/888,337, filed Jun. 22, 2001, now U.S. Pat. No. 6,535,163, issued Mar. 18, 2003 (hereafter, “Application 337”);        6. System and method to estimate the location of a receiver in a multi-path environment, Ser. No. 10/237,556, filed on Sep. 6, 2002 (hereafter, “Application 556”); and        7. System and method estimate the location of a receiver, Ser. No. 10/237,557, filed on Sep. 6, 2002 (hereafter, “Application 557”).        
The Copending Patent Applications are hereby incorporated by reference in their entireties.